Electrochemical sensors are used in devices for determining an analyte in biological samples. For determining the analyte the sensor needs to be hydrated and calibrated. The process of hydrating may also be referred to as wetting of the sensor or wet-up process.
A hot wetting process for blood gas sensor cartridges is disclosed in International Patent Application Publication No. WO 01/042473 A9. Options for accelerating the hydration of an electrochemical sensor are described. Either a sensor is wetted at an elevated temperature for, e.g., 15 minutes, in a separate device thermostated at temperatures from 55° C. to 75° C. followed by a transfer of the sensor into the instrument sample chamber, which is thermostat-controlled at a lower temperature of 15° C. to 45° C., typically 37° C. Or, the elevated temperature is applied in the measuring chamber of an analyzing device directly. Temperature changes from normal to elevated temperature can be made within 1 to 2 minutes. Although the temperature change is fast, there is a loss of period of use of the instrument, because no calibration or measurement can be performed during this time of temperature change. A calibration, performed at the elevated temperature will not be valid for measurements at a lower temperature level. With regard to sensors for which measurement functionality depends on the sensor temperature, therefore, calibrations have to be repeated at the lower temperature, or no calibration can be performed at the high level temperature. Such concerns are even more present for parameters for which measurement results have to be gathered at fixed or stable temperature conditions. Such parameters are, e.g., pH, pO2 or pCO2.
An abrupt temperature change between both temperature levels causes an obligatory instrument downtime because of the time needed to reach the new thermal equilibrium and the necessary recalibration at the new temperature level.
Also, with the hydration of the sensor matrix, a sensor signal drift is often correlated. Two restrictions are usually present for sensor signal heights. On one hand sensor signals must have a minimum signal height (above a certain signal to noise ratio) to guarantee correct results, as well as sensor signals should not exceed the range of the dynamic range of the electronic signal processing units. In either case non-calibrated sensors will not allow reproducible and reliable measurements with the sensor device.